Figure 2.

Representative frequency responses of a microbubble cavitation signal measured at different periods (before and after 3.3 ms) following ultrasound bursts. Transcranial ultrasound was emitted at 0.5 MHz into the NHP brain, and the cavitation signal was measured using a PCD transducer centered at 1.5 MHz. The occurrence of ultra-harmonic frequency components (1.5 f₀, 2.5 f₀, 3.5 f₀) is a very sudden event (<256 µs), which can occur over the burst period.